Unfortunately there is no way around returning the unit for service. Sorry.

Hi bejoro,

AFAIK you have noise reduction on "power-on" only for
- headphones outputs on all recording interfaces
- on analog outputs only for the bigger interfaces like 802, UFX, UFX II, UFX+ (+)

(+) See also my Excel Line 85 ("Damping of the switch-on crackling")
See Excel in this blog article: https://www.tonstudio-forum.de/blog/ind … B-MADIfac/
Direct link to Excel File: https://www.tonstudio-forum.de/index.ph … -04b-xlsx/

Could maybe be solved by connecting an ADI-2 DAC/Pro through ADAT (DAC+Pro) or AES (Pro only)
and assigning that channel in TM FX (UCX II) to "Main Out".

As I think that you have both devices you could try that.

Not sure about noise during sample rate changes.
Just playing a game at 44.1.
If I change the sample rate of the UFX+ (clock master) from 44.1 to 48kHz (WDM driver part),
then the sound simply turns silent, when I change it back to 44.1 the sound comes back without any noise in front of it.

Setup: UFX+ (App using WDM part of MADIface ASIO driver)  --- AES ----- ADI-2 Pro FS R BE (clock slave, through AES)
MADIface driver: 0.9736

Checked now by playing back music with MusicBee (uses ASIO driver).
No noise when switching to double or quad speed music content and back to single speed.
Finally I switched back clock rate in driver settings from double speed back to 44.1.
Short pause of around 1 sec then again sound from game through WDM driver.
When being in a different sample rate the sound from game (in 44.1) is simply turned off.

Sry, no time to check with UFX+ in CC mode or with ADI-2 Pro alone.

I will check with my UCX II, but please don't expect that before 27...

Some details of the setup:

Main out (1/2): 4 dBu
Main volume: -18 dB

Direct connection 1/2 to power amp/active monitors: 75 dB at listening position.

Good audible plopp noises at power on/power off.
Good audible crackling noises at change of sample rate (in CC mode, Linux/ALSA, in USB mode Windows/ASIO).

Audible crackling noises at change of track in CC mode Linux/ALSA, not tested on Windows.

ADI-2 PRO FS R BE is dead silent in all situations.

Thank you very much for the feedback.

The pop sound at power on/off is not disturbingly loud. I just wanted to make sure the unit is ok. There is no crackling sound at power on/off.

I had already installed the latest firmware (UCX II firmware 39/24/19 - 12/2021) and latest Windows driver 1.219. Btw, UCX II HW diagnostics still reports 24 - 2021/3 and not 2021/21 but FUT reports the actual firmware and "up to date".

Regarding the crackling sound, I tested on an RasPi4 with Linux/ALSA (mpd, upmpdcli) and on an older Notebook which I primarily use for room and speaker measurements, Windows 10 21H1, USB 2.0 only. I was playing a track with 44.1 kHz and changing to a track with 96 kHz produced a good audible crackling sound (also back or other sampling rates). Both with RasPi4 over network and Windows Notebook with JRiver MC24 from USB flashdrive (I will update to MC28 and test again).

I assume with USB subsystem you mean the USB interface and/or USB device drivers?

I will try to investigate this even more systematically and also compare to my ADI-2 PROs again.
It puzzles me that you have no crackling sound at all.

Strange, I subscribed to this thread but I do not get any e-mail notifications.

It was not my intention at all to question the quality of RME products.

I have already sold my UCX.

I will check the crackling issues again and report back.

What do you mean by "USB subsystem"?
Any hints regarding this investigation?

This kind of description is not helpful, just confusing. Changing the sample rate is not possible in the Settings dialog with a running playback. ASIO will grey out the menu, WDM will be screwed. Correct test is to have an analog input signal routed via TM FX to an analog output and listening to it. Sample rate changes should be performed in real-time by the hardware with a very short mute (0.5 s), and no crackling. Watch theTM FX level meters if the crackling is shown somewhere.

In JRiver I have a playlist with songs of different sample rates, for example 44.1 and 48 kHz, but also 192 kHz. Playing all the tracks (via ASIO) the sample rate changes in realtime as needed and with zero crackling.

If you can do none of the above then maybe the UCX II is broken.

Edit: your last comment sounds like the TM FX routing test failed...

Not sure why you think you're stupid - those were good tests. And the only explanation I have now is that the unit is indeed defective. Warranty...

No, that plus current firmware is all one can do.

I have loaded the "Factory" setup. I just used the device menu "Options - Clock" to change the sample rate and unfortunately the crackling noise still happens.

The volume of this crackling noise is independent of the volume setting of main/phones.

The volume of this crackling noise seems identical at 4 dBu and 13 dBu and is significantly louder at 19 dBu. With phones the volume of this crackling noise is lower with the "low" setting and higher with the "high" setting.

With my setup it is not only a clicking sound, it is a disturbing crackling noise. I have the UCX II directly connected to my power amps. This crackling noise might be less disturbing if you have further attenuation devices (pre amp, mixing devices) in front of your power amp or monitor speakers.

Matthias, please excuse the question, but are you clearly of the opinion that there is a hardware defect and it is not a firmware glitch?

It seems your UCX II is not defective.

The crackle of my UCX II is almost as loud as the useful signal, especially with 19 dBu or with "high" setting of the phones output.

Inspired by Andreas1 I tried another test.
Connected UCX II 1/2 OUT to Analog IN of ADI-2 PRO.

I hope I have configured this correctly. Please let me know if I my setup is flawed.
I have used DIGICheck 5.941 (Win10), it is easier to read the level meters than on the ADI-2 PRO.
Is DIGICheck fast enough to measure such short events correctly?

UCX II, Main Out 1/2: +19 dBu, Volume: 0.0 dB
ADI-2 PRO Analog IN, +19 dBu, 96 kHz (AD/DA mode), AD Filter: SD Sharp

No playback via UCX II (USB disconnected, USB mode).

Changing sample rate in device menu "Options - Clock":
Peak L: -43 dBfs
Peak R: -50 dBfs

Power ON:
Peak L: -48 dBfs
Peak R: -48 dBfs

Power OFF:
Peak L: -41 dBfs
Peak R: -43 dBfs

As said, with my power amp directly connected to the UCX II the crackle at sample rate change is very disturbingly loud, not extreme but at 4 dBu still almost as loud as the useful signal. The same for phones out (used headphones for testing: Sennheiser HD650)

I am trying to avoid having to send my UCX II back for repair or exchange because I need it very badly. But if it is defective, I will have to respond very soon, and this prolonged downtime would be a disaster.

Unfortunately not. If I could have uploaded audio files to this server, I would have done it.

@MC
Any comments about my measurements? Is the setup correct?
I could make a recording using Global Record of DIGIcheck and provide it for download.

Sorry for the delay. I am extremely busy this week.
I will make and send the recordings as soon as possible.
You will get an e-mail with download links soon.

Your recordings match exactly what I get with my unit, so yours is not broken. I have several comments:

- First of all this is a click (sample rate change) and pop (power off) sound, a single event. Crackling means several clicks/ pops over a longer time. So there never was a 'crackling noise'.

- The values noted above are peak values. The loudness of these is better represented by RMS values, which are much lower, especially with power on/off.

- The click on sample rate change happens only when changing from single to double or quad speed. 44 to 48 or 176 to 192 is completely click-free. The reason is a reset of the clocks and ADC/DAC which is unavoidable.

- I noticed a loud click when changing from 128 to 176 kHz. That seems not ok, but is not an important issue. No one has music in 64 or 128 kHz sample rate, so this setting is never used for music playback.

Which brings me back to my post 13. You clearly have a big level mismatch between UCX II and power amp, and you need to make sure your music is played at normal levels, up to 0 dBFS. If I turn up the volume at my power amps so that the mentioned noises become audible, playing music will make my ears bleed. And that is also clearly shown by the numbers that you posted. How can a click at -50 dBFS be as loud as the played music? There is something fundamentally wrong here.

I would strongly advise to try attenuators at the UCX II output if you can't reduce the sensitivity of the power amp.

Sorry, forgot the headphone:

The click of sr change over headphone changes with the output ref level (6 dB louder at High Power), because then the amp gets a 6 dB higher level from the DAC, which is the one producing the click. It is more audible with higher sensitive headphones, as the volume control is digital, so no way to attenuate this (except for using the Low Power option).

The pop on power on/off is independent from the ref level because it is coming directly from the output stage. There is no mute relais for the phones output, so a certain pop noise is expected, but low in volume, so not dangerous. This is the same as on all our other interfaces. The volume of that pop depends on the used headphone. Low sensitivity ones show less pop (barely audible).

Please note the UCX II is not a HiFi oriented unit (as the ADIs) for totally click/pop free home use, but a production tool for the studio/music making. As such cost and space consuming features like headphone output relais are not part of this (all these) products.

A question: At SR 44.1 or 48 The analog input meters linger between -102 and -104 when setting SR 192 they are between - 77 and -79 nothing connected?

Takk Andreas! Jeg hadde det et sted i bakhodet. Får visst ikke lest den manualen mange nok ganger

Do the UCX II analog outputs have power-on pop suppression? How does it compare with the UFX II/+?

Got it, many thanks, that answers my first question. Do you know if the UFX II and the UCX II use the same pop suppression technology? In other words, are there any differences in the quality of the power-on pop suppression between these two models?

Off-topic but why not put your list on Google Sheets? It's so much easier to work with than Excel, especially for searching text, and users could bookmark your document which means any changes you make are immediately available to everybody who has the link. This eliminates the need for users to scour the forum for a link to the (hopefully) latest version of the Excel file. Besides, Google Sheets has built-in version control, which should make your life easier.

Fair enough, although you could still work in Sheets and download the file as .XLSX once every month just to have a safe local copy. I mean, it's not sensitive data since you are sharing it publicly, and you can't prevent anyone from uploading your file to Google Sheets and sharing it that way (hopefully crediting you for the work). I think most people would prefer the Google Sheets version for the convenience—just my 2c. Regardless, nice work.

(anyway, forget that, let's stay on-topic)